When a drug solution is administered to a patient for example, a blood vessel of the patient is punctured by a hollow needle to perform it. As a medical instrument by which such a procedure can be carried out, one is known that has a syringe unit composed of a cylindrical body in which a drug solution is filled and a hollow needle mounted at a distal part of the cylindrical body, a cylindrical casing that houses the syringe unit movably, and an operation button that is provided at a proximal part of the casing and is to carry out start operation of actuation of the syringe unit (for example, refer to Patent Document 1). In the medical instrument described in this Patent Document 1, the syringe unit can move to a first position at which the hollow needle protrudes from a distal opening of the casing and a second position at which the hollow needle is retracted to a position closer to a proximal side than the distal opening of the casing.
However, in the medical instrument described in Patent Document 1, although the syringe unit returns to the second position after use thereof, possibly this syringe unit unintentionally moves to the first position because being not surely fixed at the second position. In this case, there is a problem that a hand finger or the like is accidentally punctured by the protruding hollow needle.
Furthermore, when a drug solution is administered by using the medical instrument described in Patent Document 1, the casing needs to be grasped and a pressing operation of a syringe button needs to be carried out with the casing grasped. Therefore, corresponding to the existence of the syringe button, a structure of this medical instrument is complicated, which possibly causes failure. Moreover, in the pressing operation of the syringe button, the user is caused to feel fear at the time of the use by operation sound and movement sound of the syringe unit or e.g. difficulty in grasping what movement speed the syringe unit moves at for puncturing by the hollow needle, so that the user hesitates to use it. That is, there is also a problem that this medical instrument is inferior in the operability.
Patent Document 1: JP-T-2010-532243